File Extensions

As you explore the contents of your computer, you will see thousands of files. Each of these files serves its own unique purpose and each has both a name as well as a file extension. File extension are simply the last set of characters after the period of a file name. For example, if you have a file called “setup.exe”, the file extension is “exe.” Likewise, a file named “report.xls” has a file extension of “xls.”

The file extensions give you a clue as to the purpose of the file as does the name in many cases. An EXE file extension is an executable, or a program. From the name “setup.exe” we can guess that this is the executable that will setup or install a particular program. When seeing a file called “report.xls”, the XLS file extension tells us that it is a Microsoft Excel spreadsheet. The name “report” would have been assigned by the user to describe the spreadsheet’s purpose or contents.

Because there are thousands of file extensions, it’s impossible to know what each one means. You may recognize the ones you work with on a daily basis such as DOC (Microsoft Word), XLS (Microsoft Excel), and PDF (Adobe Reader). Others are less common. With that in mind, we have deciphered the file extensions.

If you can’t see the file extensions of your own files, there’s a simple fix. In Windows XP, open the My Computer folder, select Tools, Folder Options, and click on the View Tab. Scroll down to “Hide file extensions for known file types” and remove the check mark in the box. Click on Apply to All Folders and close the window.

In Windows Vista, go to Computer, click on Organize and then Folder and Search Options. Click the View tab. Once again, scroll down to “Hide file extensions for known file types” and remove the check mark in the box. Click on Apply to All Folders and click OK.

What are file extension errors?

File extension errors are common, especially when your computer doesn’t recognize the extension or is set to use the wrong program to open it. For example, if you have a certain program you use at your office to create documents and you decide to do a little work you’re your home computer, you may run into a file extension error. If your home PC doesn’t recognize the file extension or have the appropriate program installed, it won’t be able to open it.

Other file extension errors occur when you have the correct program installed however Windows doesn’t know to associate the file extension with that particular program. For example, some software programs change the computer’s file association settings to make their program the default application for a particular file association. You may be able to open the file but with the wrong application or if you’ve uninstalled the application, you may receive file extension errors.
Changing file associations can overcome many common file extension errors. Each computer program you have installed on your system is set to open a particular file type which is identified by the file extension.

For example, Microsoft Word opens DOC file extensions. In addition, some file extensions can be opened by many different programs in which case one program is set as the default program for that file type. For example, Windows Media Player and Apple QuickTime are both able to open M4A files. Depending on your system, one of these two programs (or some other program) may be the default program for opening this file extension.

To change a file association, find a related file and right-click it. Click on Properties. Click on Open With. Click on Choose Default Program. A list of suggested programs will appear. Choose the program you want to use to open this file type. Place a check mark in the box saying, “Always use the selected program to open this kind of file.”

Other file extention errors involve spyware, computer viruses, and other malicious programs. Common file extensions you should beware of include: .exe, .com, .pif, .bat, .scr, and files with two extensions such as document.txt.exe. To avoid security breaches, make sure to keep your anti-spyware and anti-virus programs activated and current.

Another way to avoid file extention errors is to keep your system and regular software programs current and updated with the latest patches and updates. These updates, whether from Microsoft or other vendors, often address known issues with file extensions.

Finally, file extention errors can start in the Windows registry. Missing shortcuts, file corruption, and invalid file associations often have their beginnings in the registry and instruct your operating system with the wrong information. To rule out a registry-related file extension error, run our free scan.